Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$182.93	4.255%	$190.7137	$190.71	$190.70	$190.70
Purchase #2	$7.27	13.830%	$8.2754	$8.28	$8.30	$8.30
Purchase #3	$83.35	6.157%	$88.4819	$88.48	$88.50	$88.50
Purchase #4	$136.50	10.600%	$150.969	$150.97	$150.95	$151.00
Purchase #5	$126.96	10.194%	$139.9023	$139.90	$139.90	$139.90
Purchase #6	$50.68	6.260%	$53.8526	$53.85	$53.85	$53.90
Purchase #7	$76.56	9.406%	$83.7612	$83.76	$83.75	$83.80
7 purchase totals =	$664.25		$715.9561	$715.95	$715.95	$716.10